No is not a four letter word.

Self-described people pleasers find it hard, if not impossible, to say no.  Their anxiety often centers around the potential for losing out on a future opportunity.

"If we don't solve this problem for the customer, they won't buy other services from us later."

"I really should take on the new project because I won't get an opportunity like this again."

Whether we are "shoulding" on ourselves or letting others "should" on us, why is the reason to say yes based only on the future positive outcome (future new business or future project offers)?  There are an infinite number of outcome possibilities, but it's the worry of marginalization, the fear of insignificance, that drives the decision.

Don't be bullied.  Be decisive.